It will show you how the system has been programmed, under card configuration on the easy edit menu it will show which cards are in the programming on the system, but this is only how it has been programmed and doesnt mean there is definately an op box or ISDN BRI card installed.
To be certain it would be best to speak to someone on site and get them to look at the equipment and see if there is an expansion cabinet on the right hand side.